The Whites Bridge fire has been declared an act of arson by the state's fire marshal, according to Ionia County Sheriff Dale Miller.

Miller said a lab report indicated an accelerant was found at the site of the fire, which destroyed the 146-year-old, covered wooden bridge, one of Michigan's oldest, early July 7. Evidence collected from the bridge was analyzed in the Michigan State Police crime lab and tested positive for an accelerant.

The investigation is continuing, and law enforcement is following up on all leads, said Miller.

"We don't have any strong leads at this time, so we are asking the public's assistance," he said.

There is currently a $7,000 reward for information leading to the arrest and conviction of a person or persons in this case.

Anyone with information should call the Ionia Sheriff's Office at 616-527-5737 and ask for the detective bureau or call the Silent Observer hotline at 616-527-0107. Citizens also can call the Arson Tip Line at 1-800-44-ARSON (1-800-442-7766).